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Subject: Re: [boost] CMake and Boost Build tests
From: Edward Diener (eldiener_at_[hidden])
Date: 2017-07-27 14:45:25

On 7/27/2017 8:12 AM, Florent Castelli via Boost wrote:
> On 27/07/2017 10:24, Edward Diener via Boost wrote:
>> On 7/27/2017 1:12 AM, Robert Ramey via Boost wrote:
>>> On 7/26/17 7:28 PM, Edward Diener via Boost wrote:
>>>> But the case I brought up is that there is no "build' of the
>>>> library, since it is header only, but the library needs to execute
>>>> its tests using CMake. That appears to me to be different from your
>>>> case.
>>> Well, there is the safe numerics library which has CMake tests and is
>>> header only. It's much simpler than the serialization library.
>>> You'll find a few CMakeLists.txt files in different places like
>>> include/example/test etc. Not that much unlike bjam where one has
>>> jam files in test, example, etc.
>>>> So you are saying that even when their is no actual library to be
>>>> built, as is the case with a header only library, you still specify
>>>> a CMakeLists.txt file as if you were building a library ?
>>> yep - just like for bjam you specify a jam file in the test
>>> directory, for CMake you specifiy a CMakeLists.txt file in the test
>>> directory.
>> Great, thanks !
>>>>> This is a serious short coming of CMake. Given this it's a mystery
>>>>> that CMake has been successful. But then then look at all the
>>>>> competition it's ever worse!!! To addressed this, I wrote a walk
>>>>> through in the boost library inclubator to help library developers
>>>>> get started with CMake. It uses on the safe numerics library CMake
>>>>> as an example. This example/narrative addresses only header-only
>>>>> files.
>>>> Would you please give a URL ?
>>> I'm really disappointed you couldn't find this. It recently was
>>> reviewed for inclusion in boost and accepted!
>> You said you wrote a walk through in the boost library incubator and I
>> asked for the URL of the walk through. You gave me a link to your safe
>> numerics library on github. I have found
>> I will read this.
>>>> Do you know if CMake has a way of setting usage requirements for all
>>>> builds in a directory ? That is the effect of the project rule in
>>>> Boost Build when running tests. It is very useful and means that you
>>>> do not have to repeat a bunch of usage requirements for each and
>>>> every test.
>>> Right. Every build system has to address this problem.
>>> In bjam I can make a "rule" which passes "usage requirements".
>> You do not have to make a rule since the builtin "project" rule
>> already does this for you.
>>> In CMake I make a "function" which passes arguments.
>> So CMake has no way built-in command to say "here are the usage
>> requirements for every target in this directory" other than to have to
>> write a "function" each time ? That seems a bit poor.
> It does has some support for things like that, but it scales poorly.
> What you can do instead is have a target with all the requirements you
> want and link against it and they will bubble up.
> Or you just use a function, which is not a bad thing, they can remove a
> lot of boilerplate and make the intent clearer.
> Would you write ASM all the time? No, you write high level C++. A build
> system is no different.

What would be the CMake syntax for such a target ? In Boost Build the
'project' rule lets you set requirements. How would I do that with your
target. Some CMake code please ?

>>> Similar but different. For some reason every build system designer
>>> seems to fancy himself a language designer and what we get is some
>>> oddball/irregular "language" for describing the "build". When it
>>> barely works the release and then start patching it up to so it can
>>> be made to work. The result is what we have to today. An assortment
>>> of build languages none of which are very good. This is addressed by
>>> inventing a NEW build language which isn't really any better than the
>>> one it's meant to replace. This happens again and again - this is
>>> how we came to be where we are today.
>>>> I will look at your serialization CMake code and I assume the other
>>>> working example is for your Safe Numerics library, so I will look at
>>>> that also. Thanks !
>>> There are other examples already in boost - made by people who know
>>> more about CMake than I do. (I hate wasting time on this kind of
>>> stuff). Unfortunately, many of these examples seem to be more
>>> elaborate than necessary and end up totally obscuring that which
>>> starts out simple. Its a chronic programmer disease to start with
>>> something understandable which works and then try to make it perfect
>>> there by mucking it up. Hollywood plastic surgeries have the exact
>>> same problem.
>>>>> I've got a lot to say about this and I will be giving a
>>>>> presentation on the subject at CPPCon 2017 for anyone who might be
>>>>> interested. That is the both of you.
>>>> I did not realize I was a split personality <g>.
>>> Hmmmm - It didn't occur to me that you might be going to CPPCon. So
>>> I guess I'll plan for three then.
>> No I don't go to CPPCon but if you can get programmers to create
>> better documentation by your talk there I am all for it.
>>> Robert

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